Heat treating furnace with shielding packs



E N I 9 52 f l July 22, 1969 J. R. BORNOR 3,456,935

HEAT TREATING FURNACE WITH SHIELDING PACKS Filed Sept. 20, 1967 4Sheets-Sheet 1 38 i t 439 40 41 4o 65 9 h a M 32 s 32 49 H r MVEMTO K)um? IQl'G/W P j 4, 1, W/ f July 22, 1969 J. R. BORNOR 3,456,935

HEAT TREATING FURNACE WITH SHIELDING PACKS Filed Sept. 20, 1967 4Sheets-Sheet 2 @M, WVJJM @TTOFZADETYf y 9 J. R. BORNOR 3,456,935

HEAT TREATING FURNACE WITH SHIELDING PACKS Filed Sept. 20, 1967 4Sheets-Sheet 5 dune @[Ja/d 60/770! MQM,

d-r'rOJQADEZYJ July 22, 1969 J. R. BORNOR 3,456,935

HEAT TREATING FURNACE WITH SHIELDING PACKS Filed Sept. 20, 1967 4Sheets-Sheet 4 W Q10" 6 Q EOI'WOI @qT'romoaY/ United States Patent3,456,935 HEAT TREATING FURNASJE WIII-I SHIELDING PAC June RichardBornor, Rockford, IIL, assiguor to AIco Standard Corporation, Cleveland,Ohio, 2 corporation of Ohio Filed Sept. 20, 1967, Ser. No. 669,172 Int.Cl. F23m 9/00; F2711 21/00 U.S. Cl. 263-40 30 Claims ABSTRACT OF THEDISCLOSURE A vacuum heat treating furnace having a water-jacketedvacuum-tight vessel with a radiation-shielded inner enclosure defining aheating zone inside the enclosure and a cooling zone between theenclosure and the vessel. The enclosure is formed with inlet and outletports for the circulation of quenching gas by a fan outside theenclosure, and the radiation shielding is formed by independentlyremovable shielding packs each having a series of spaced shields on asupport constituting the outer member of the pack, the shields beingcarried on pins projecting inwardly through the shields with spacersleeves between adjacent shields, and the spacers being Coils ofmolybdenum wire. Rectangular packs shield the cylindrical sidewall ofthe enclosure, and packs in the form of segments of a circle form theend walls, the segments being truncated to define the ports. Movablereflectors close the ports during heating and are retracted duringcooling, the heating being accomplished by ribbon elements extendingzigzag fashion along the cylindrical wall and mounted on hangersextending through the shielding. In the alternate form, the rectangularsupports and the shields are arcuately curved and interfitted togetherin selfsustaining cylindrical shape.

BACKGROUND OF THE INVENTION This invention relates generally to heattreating furnaces and, more particularly, to vacuum furnaces for heatingworkpieces in a heating chamber or zone and subsequently cooling theworkpieces by circulating a cooling gas through the zone and around theworkpieces therein. Furnaces of this general type are disclosed in IpsenPatent Nos. 3,301,541 and 3,219,331 wherein it will be seen that thebasic furnace structure includes a vacuum-tight vessel with an internalenclosure defining the heating zone and forming a heat barrier forconfining heat within the zone around the work therein. The enclosure isformed with ports for the circulation of cooling gas into and out of thezone, and a fan is provided, outside the enclosure, for drawing hot gasout of the chamber through one port and forcing it around the enclosurethrough a cooling zone and back to the other port for recirculationthrough the chamber. To limit loss of heat through the ports, the latterare covered during heating, either by fixed bafiles or by movablereflectors, as disclosed in the aforesaid patents.

The invention has particular reference to the construction and supportof the heat barrier in the vessel. The above patents utilize innerheat-resistant walls backed by conventional insulation, while othershave suggested the use of spaced radiation shields encircling theheating zone to reflect the heat back toward the work. The problem withthis type of barrier, however, is the difiiculty and expense involved inthe initial installation of the shields and the maintenance of theshields in service use, particularly when the shielding is composed ofthe thin foil that is preferred to reduce the amount of heat stored inthe shielding.

Patented July 22, 1969 iCC The primary object of the present inventionis to proi vide a shielded heat treating furnace which overcomes theprimary objections to prior shielded furnaces by greatly simplifying theinstallation and replacement of shielding in the furnace while providingan effective heat barrier in service use. A more specific object is toprovide a novel type of shield pack that is relatively simple andinexpensive to construct, and to form the heat barrier within thefurnace with a plurality of such packs arranged around the heating zone.Other objects are to construct and mount the packs for relatively quickand easy installation and removal, to shape and arrange the packs in anovel manner for use in a cylindrical furnace to cover not only thecylindrical wall but also the end walls, and to construct the packs assimply and inexpensively as is possible for independent handling asself-sustaining units. The invention also resides in the novel andsimple manner of supporting the packs in the furnace for easyinstallation and removal.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a fragmentarycross-sectional view taken in a vertical plane through a heat treatingfurnace embodying the novel features of the present invention andshowing the furnace in condition for a heating operation, the positionof a work load being indicated in broken lines.

FIG. 2 is an enlarged cross-sectional view taken substantially along theline 22 of FIG. 1.

FIG. 3 is a fragmentary view of part of FIG. 2, on a greatly enlargedscale, and showing the details of construction and mounting of thepacks.

FIG. 4 is a perspective view of one of the shield packs used to coverthe sidewall of the chamber.

FIG. 5 is an exploded perspective view of one of the packs used to coveran end wall of the chamber.

FIG. 6 is an enlarged fragmentary cross-sectional view takensubstantially along the line 66 of FIG. 4, and showing details ofsupport of the shields of a pack.

FIG. 7 is an enlarged cross-sectional view similar to part of FIG. 1.

FIG. 8 is an enlarged fragmentary cross-sectional view takensubstantially along the line 88 of FIG. 1.

FIG. 9 is an enlarged fragmentary cross-sectional view generally similarto FIG. 3 and showing an alternate form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings forpurposes of illustration, the invention is embodied in a furnace 10 forheating workpieces 11 (FIG. 1) in a chamber or zone 12 defined by acylindrical enclosure 13 oriented about a vertical axis and disposedwithin a vacuum-tight vessel 14 having a cylindrical inner wall 15, andsubsequently cooling or quenching the work in the heating chamber toobtain desired physical properties of the metal. To protect the finishof the workpieces, they are heated in a protective atmosphere such as avacuum produced by a suitable pumping apparatus 17 that communicateswith the interior of the vessel through a port 18, and are quenched in aflow of non-oxidizing gas admitted into the vessel through a port 19from a source such as a pressurized tank (not shown).

During treatment, workpieces are supported in a hearth 20 adjacent thelower end of the work chamber 12 and are surrounded by radiant heaters21 connected through the lower end wall 22 to a suitable electricalsource and control. Cooling gas is circulated within the vessel uponcompletion of heating by a fan 23 disposed beneath the upper end wall 24of the vessel and driven by a motor 25 Outside the vessel. It will beseen in FIG. 1 that the cylindrical enclosure 13 includes a cylindricalshell 13 supported in spaced relation with the vessel wall 15 to definea cooling zone 27 outside the enclosure, and that inlet and outlet ports28 and 29 are formed in the end walls of the enclosure on opposite sidesof the heating zone, the outlet port being immediately beneath the fanso that heated gas drawn out of the chamber by the fan is forcedradially outwardly and then downwardly through the cooling zone and thenis forced back into the chamber through the inlet port to flow throughthe chamber and around the work. Baflles or movable reflectors 30 and31, herein the latter, block heat radiation through the circulationports during heating but permit gas circulation during quenching, asdescribed in the aforesaid patents.

In this instance, the vessel 14 is surrounded by a water jacket 32 inwhich coolant is circulated during operation of the furnace, the innercylindrical wall 15 thus constituting a cooling element as well as theouter wall of the interior of the furnace. Other cooling elements suchas coils or fins in the cooling zone may be used to assist in coolingthe circulating gas. Herein, the outside of the cylindrical enclosure 13is wrapped with coolant-circulating tubes 33. For access to theinterior, the upper section of the vessel is removable, the two sectionsof the water jacket being separated by rings 34 which are clampedtogether when the furnace is closed. The fan motor 25 is mounted on apad 35 recessed into the upper end wall 24 of the vessel, and the upperend wall of the enclosure 13 is supported on the upper section of thevessel for removal with the upper section, thus opening the enclosurefor loading and unloading of workpieces as an incident to the opening ofthe vessel. For this purpose, the upper end wall is suspended from thetop section of the vessel on a perforated wall 37 fastened to the topsection.

The upper reflector 31 is a disk-shaped piece larger in diameter thanthe outlet port 29 and overlying the latter within a hood 38 having anoutlet 39 adjacent the underside of the fan. Supporting the reflectordisk is a horizontal track 40 and a rod 40:: which extends horizontallyto the right, as viewed in FIG. 1, through the sidewall 15 of th vesselto a cylinder 41 for shifting the reflector into and out of its blockingposition over the outlet port. The hood and a sealed extension casing 42thereof define a chamber at 43 spaced to the right from the port forreceiving the reflector in its out-of-the-way position in which the portis uncovered.

Similarly, the lower reflector 30 is a disk fitted upwardly into theinlet port 28 of the enclosure and movably supported on a vertical rod44 extending downward- A ly through the lower end wall 22 of the vesselto a cylinder 45 for lowering the disk from the raised position shown inFIG. 1 to a lowered, out-of-the-way position adjacent a ring 47 on thelower end wall. Thus, both ports may be closed during heating and thenopened wide for full circulation of cooling gas through the work chamber12. A downward extension 48a of the outer cylindrical wall 48 of thewater jacket forms a base for the furnace, the lower end of the waterjacket being formed by a dished disk 49 sealed at 50 to the sidewall.

For optimum operating efliciency, a heat barrier is formed between theheating and cooling zones 12 and 27 to limit the escape of heatgenerated by the heaters 21. This not only concentrates available heaton the work in the heating zone but also facilitates cooling ofcirculating gas in the cooling zone for more rapid quenching of thework. In prior practice, both insulated walls and groups of reflectingshields have been used for this purpose, with varying degrees of successand practicality in service use.

In accordance with the present invention, the heat barrier between theheating and cooling zones 12 and 27 is formed by a plurality ofshielding packs 51 and 52 that are comparatively simple and inexpensiveto construct and are arranged in groups covering the various walls ofthe heating zone, forming substantially continuous inner reflectingwalls backed up by spaced reflecting walls each formed by severalreflecting sheets of different shielding packs. The packs are supportedin a novel manner in the furnace in edge-to-edge relation such that thebarrier is as effective as that obtained with prior conventionalshielding while the packs are much easier to work with, both duringinitial installation and during eventual maintenance of the furnace.

In this instance, the cylindrical shell 13a has an open upper endcovered by an annular upper wall of shielding defining the outlet port29, and has an apertured lower end wall 53 beneath an annular lower wallof shielding defining the inlet port 28. The annular walls of shieldingare formed by the packs 52 and the cylindrical sidewall is covered bythe packs 51. For this purpose, each of the packs 51 is of elongatedrectangular Shape, as shown most clearly on FIG. 4, and comprisesseveral fiat rectangular sheets 54 of reflecting material, for example,thin and flexible molybdenum foil, arranged in spaced, side-by-siderelation alongside an elongated shape-retaining support in the form of arectangular plate of channelshaped cross-section having a flat body 55parallel to the outer sheet of the pack and flanges 57 along itslongitudinal margins extending outwardly away from the sheets.

The sheets 54 of each pack 51 are held on the associated support plateby a plurality of pins 58 fastened to the body 55 and extending inwardlytherefrom through all of the sheets, and are maintained in properlyspaced relation by means of washers 59 on the inner ends of the pins andspacer sleeves 60 (FIG. 6) of preselected length that are telescopedonto the pins between the sheets and abut against the latter around theholes through which the pins project. A lock wire 61 inside each washerholds the latter in place on the supporting pin, and a fastener 62 onthe plate body cooperates with the outer spacer sleeve on each pin tohold the outer sheet 54 in properly spaced relation with the plate. Asshown in FIG. 6, the fasteners herein are so-called rivnuts into whichthe pins are threaded, the rivnuts having heads disposed inside theplate, riveted shoulders outside the plate and tapped center bores intowhich the pins are threaded.

In the illustrative packs 51, five vertically spaced pairs of pins 58are provided on each support plate with the pins of each pair positionedadjacent the opposite longitudinal edges of the sheets. The packs aresomewhat shorter than the length of the shell sidewall 13a, covering thelatter completely between the upper and lower shielding walls, and areof preselected width such that a predetermined number of packs may bearranged edge-to-edge as shown in FIG. 2 to surround the chamber 12 witha heat barrier of polygonal cross-sectional shape. Of course, the shape,length and Width of the packs may be varied to suit different sizes andshapes of heating chambers and, while flat sheets are easiest to workwith, other shapes may be used. At least the inner sheets of the packshould be capable of withstanding the maximum operating temperatures tobe used, but the outer sheet or sheets and the support plate, beingprotected by the inner sheets, may be composed of materials such asstainless steel suited for lower temperatures.

To support the packs 51 inside the cylindrical shell 13, brackets 63(FIG. 3) in the form of L-shaped plates are arranged in pairs andfastened to the shell as by rivets 64 with the free legs of the bracketsin each pair projecting inwardly, parallel to each other and spaced tolie alongside the flanges 57 of a support plate, herein between theflanges. Bolts 65 fasten each pack removably to a pair of bracketsadjacent the upper end of the shell where the bolts are easilyaccessible for installation during assembly and also for removal duringlater maintenance. Similar brackets (not shown) below the'upper pairguide or brace the lower portion of the pack to hold it in an uprightposition along the cylindrical shell wall.

Initially, the pairs of brackets 63 are spaced according to the width ofthe packs 51 and a full set of packs is installed simply by positioningeach pack along the wall and over the brackets and bolting the upperends of the brackets. If, in service use, it should become necessary toremove a pack for repair or replacement, the old pack is unfastened andpulled endwise out of the shell and the replacement is slid endwise intothe vacated space and bolted in place. Supported in this manner, thepacks are free to grow and contract in length during heating andcooling.

As shown in FIGS. 2 and 3, at least the inner sheets 54, and preferablyall of the sheets, overlap the corresponding sheets of the packs on eachside. Herein, all of the sheets are overlapped and, due to the angularrelationship of adjacent packs, the inner sheets overlap each other to agreater extent than the outer sheets. With this progressive overlap allthe sheets in each pack may be the same size for ease in construction.

To complete the reflecting heat barrier around the heating zone 12, theupper and lower walls of the enclosure 13 are formed as rings by twogroups of shielding packs 52 which are generally in the shape oftruncated sections of a circle, as shown most clearly in FIG. 5, eachhaving several sheets 67 of reflecting material supported in spacedside-by-side relation on pins 58 on a channel-shaped plate 69. As in thepacks 51, the pins are mounted on the support plate by means of rivnuts62 and carry spacer sleeves 60 holding the sheets in properly spacedrelation. The structure shown in FIG. 6 applies equally to both types ofpacks.

The arcuately curved inside edges of the sheets 67 define the ports 29and 30 and the outside edge portions overlie the upper and lower edgesof the sheets 54 of the packs 51 to eliminate straight-line pathsthrough the bar rier where the two types of packs come together, the

various edges preferably being staggered as shown in FIGS. 1, 4 and 5.When light and freely flexible foil sheets are used, the edges of thesheets at the ports preferably are capped with flanged rings 70 and 71,as shown in FIG. 1, to prevent fluttering of, and possible damage to thesheets during gas circulation. The support plates of the lowerreflecting wall of the enclosure are attached to the lower end wall 53of the shell, and the supports of the upper reflecting wall are boltedto brackets on the wall 37 and thus are mounted for movement with theupper section of the vessel. Each of the reflecting disks 30 and 31 isformed as a series of spaced shields suitably mounted for movement as aunit by the cylinder 41 or 45. If foil sheets are used, the edges ofthese sheets are capped to reinforce the sheets around the peripheriesof the disks.

As will be seen in FIG. 1, the hearth is formed by horizontal barssupported on posts 72 upstanding from the end wall 53 of the shellthrough holes in the sheets of the lower shielding packs 52, and thecircuits for the heating elements 21 include leads 73 entering throughthe lower end of the vessel and extending into the heating zone throughthe end wall of the shell and the packs 52. The holes in the packs 52may be performed in appropriate locations for the various elements thatproject into the heating chamber through the shielding.

Herein, the heating elements 21 are upright portions of one or moreelongated ribbons of suitable resistanceheating material connected tothe leads 73 and extending zigzag fashion up and down along the innerreflecting wall formed by the inner sheets of the packs 51. Each ribbonextends upwardly along the reflecting wall parallel to the latter asshown in FIG. 1, then passes over a hanger Y 74 as shown at 75 (FIG. 7)adjacent the upper end of the pack, and then extends vertically backdown along the reflecting wall to a level near the lower end of thepack, crossing over to the next upwardly extending portion in front ofthe next pack 51. The hangers 74 comprise rods 77 (FIG. 7) threaded intorivnuts 78 anchored in the sidewall 13 of the shell and projectinginwardly through the shielding packs to upwardly extending, downwardlyhooked inner end portions 79 spaced inwardly from the heating elements.The ribbon position 75 passes over an insulating ceramic spooltelescoped onto each hanger rod adjacent the hook 79, the spoolcomprising two flanged end pieces 80 separated by a spacer S1 and beingheld on the hanger rod between a retaining plate 82 and an elongatedinsulating sleeve 83 covering the hanger rod between the spool and theshell. A brace 84 is fastened to ring 85 on the upper end of the shellsidewall above the pack and extends downwardly and inwardly to the innerend of the hanger rod with a hook 87 interfitting with the hook 79 tobrace the hanger against sagging, in the manner of a guy wire.

The lower portions of the heating elements 21 are braced laterally bylower hangers 88 (FIG. 8) disposed between adjacent packs 51 andincluding rods 89 secured to the shell sidewall and extending inwardlythrough the shielding with insulating tubes 91 on their inner endsabutting against the adjacent sides of two heating elements. Wires 92hold the elements adjacent the tube ends, and a ceramic sleeve 93 coversthe rod and holds the tube against a washer 94 to maintain the spacingof the heating elements from the inner sheet of shielding. The outer endportions of rods 89 extend loosely through flanged sleeves 95 fitted inthe sidewall 13 and are held in place by bolts 97, which can be removedfrom outside the shell to release the hanger. In this manner, theheating elements 21 are supported securely on the shell and maintainedin properly spaced relation with the shielding.

Although the lower hangers 88 extend through the portion of theshielding where the sheets 54 of adjacent packs 51 overlap, it ispreferred to provide preformed holes for the hangers. Similarly, holesare preformed for the upper hangers 74 adjacent the upper ends of thepacks. The brace rods 84 may extend through the overlapped jointsbetween the packs 51 and the upper packs 52.

DESCRIPTION OF ALTERNATE FORM, FIG. 9

Shown in FIG. 9 is a modified form of the invention in which the sheets98 of the shield packs 99 are curved to follow the curvature of acylindrical vessel inside the latter. In this instance, the sheets ofeach pack are mounted on a curved support plate 100 by means of socalledpigtail hanger pins having integral loops 101 on their inner endsabutting against the inner sheet of the pack with shanks 102 extendingoutwardly through aligned holes in the the sheets and the support plate.Push nuts 103 on the outer ends of the pins hold the latter in place,and spacer sleeves 104 between the layers of shielding, and between theouter sheet and the support plate, maintain the spacing of the sheets.

Again, the sheets of adjacent shielding packs overlap to form a completereflecting barrier. It will be seen that the supports and sheets ofthese packs have rectangular outside shapes, and that the sheets and thesupports are concentrically curved to form sections of cylinders.

Another modification in FIG. 9 is the manner of holding the supportplates 100 relative to each other. Instead of fastening the plates to anouter shell member, the plates are formed with interfitting elements 105and 107 along adjacent side edges for coupling adjacent packs 99releasably to each other whereby the supports them selves form acylindrical shell. Herein, the elements 105 are laterally opening,U-shaped channels secured to corresponding edges of the packs, theright-hand edges as viewed in FIG. 9, to receive and interlock withedging strips 107 on the left-hand edges of the adjacent packs, theedging strips being clamped around the left edge portions. With thisarrangement, the packs are fitted together in edge-to-edge relation withthe shielding sheets 98 overlapping each other, and are self-sustainingin a cylindrical shape. At the same time, any pack or packs may bewithdrawn endwise from the cylinder and replaced in generally the samemanner as in the first embodiment.

From the foregoing, it will be seen that the present invention overcomesthe primary disadvantages of prior shielded furnaces by providingeasy-to-construct packs of shielding that may be fitted together to makea complete heat barrier, and that are independently separable from theremainder for repair or replacement. Accordingly, individual reflectingwalls of different shapes and sizes may be constructed by arranging aplurality of packs of preselected size and shape in the particular shapeof wall that is needed, and holding the packs in the desired shape in amanner that facilitates removal of any selected pack or packs forservicing.

I claim as my invention:

1. In a heat treating furnace, the combination of, a vacuum-tight outervessel; a cylindrical shell inside said vessel surrounding a heatingzone inside said shell; means supporting said shell in spaced relationwith the vessel; a series of first independently separable shieldingpacks arranged around and covering the inner side of said shell, each ofsaid packs comprising a plurality of generally rectangularheat-resistant reflecting sheets spaced apart in side-by-side relation,a support between the outer sheet of each pack and said shell, aplurality of pins on said support extending inwardly therefrom throughsaid sheets, and spacing means on said pins maintaining said sheets inspaced relation with each other and with said support; means releasablysecuring each of said supports to said shell and thereby mounting saidpacks on the shell whereby each said pack may be independently installedand removed, said packs being mounted in edge-to-edge relation to form agenerally cylindrical heat barrier inside said shell; second shieldingpacks forming end Walls disposed across the ends of said heating zoneand having central openings for the circulation of gas through the zone,said second shielding packs similarly comprising a plurality ofheat-resistant reflecting sheets spaced apart in side-by-side relation,a support between the outer sheet of each pack and the adjacent end ofsaid vessel, pins on said support extending inwardly through the sheets,and spacing means on said ins maintaining said sheets in spacedrelation; means securing the supports of said second packs in place withthe shields thereof in edge-to-edge relation with said first packs,whereby said first and second packs subsentially enclose said heatingzone; and means in said zone for heating workpieces. I

2. The combination defined in claim 1 in which each of said end wallscomprises a plurality of second packs constituting parts of a ring, thereflecting sheets of each of said second packs being in the shape oftruncated rectors of a circle with outside edges in overlapping relationwith the end edges of said rectangular sheets and with inside edges atsaid openings, the securing means for said second packs includingmembers extending across both ends of said shell outside said end walls.

3. The combination defined in claim 1 in which the sheets of said firstpacks are subsentially flat and extend along chords of said shell,forming said barrier with a polygonal cross-section to surround saidheating zone.

4. The combination defined in claim 3 in which each of the supports ofsaid first packs is a rectangular plate of channel-shaped cross-sectionhaving a body lying alongside the outer sheet of the package and flangesprojecting outwardly toward said shell, said securing means comprisingbrackets fastened to said shell and to said flanges.

5. The combination defined in claim 4 in which said brackets arearranged in planes parallel to said flanges and are spaced apart to abutagainst the sides of the flanges.

6. The combination defined in claim 1 in which said spacing meanscomprise a series of spacer sleeves telescoped onto said pins anddisposed between adjacent sheets thereon in abutting engagement with thesheets, and abutments on the inner ends of said pins retaining the innerreflecting sheets thereon, said sleeves being composed of heat-resistantwire wound into helical coils.

7. The combination defined in claim 1 in which said first packs arepositioned with the reflecting sheets thereof overlapping the sheets ofthe adjacent first packs on both sides.

8. In a heat treating furnace of the type having an outer wall, an innerheating zone, means in said zone for heating workpieces to be treated,and a heat barrier between said outer wall and said heating means, theimprovement comprising a plurality of independently separaable shieldingpacks arranged around said heating zone to form said barrier, each ofsaid packs comprising a plurality of sheets of heat resistant reflectingmaterial in spaced apart, side-by-side relation, an outer support foreach pack disposed alongside the outer one of said sheets, pins mountedon said support and extending inwardly through said sheets, and spacingmeans on said pins maintaining said sheets in spaced relation with eachother; and means for mounting said supports in said furnace, said packsbeing disposed in edge-to-edge relation to surround said zone with theinner sheets of the packs forming a substantially continuous reflectingwall defining the sides of said zone and said packs being removable andreplaceable independently of each other.

9. The improvement defined in claim 8 in which said spacing meanscomprise a series of spacer sleeves telescoped onto each pin anddisposed between adjacent sheets thereon in abutting engagement with thesheets,

and an abutment on the inner end of each pin retaining the inner sheetthereon, each of said sleeves being composed of heat-resistant wirewound into a helical coil.

10. The improvement defined in claim 8 in which each of said supports isa plate of channel-shaped cross-section having a body lying alongsidesaid outer sheet and flanges projecting outwardly toward said outerwall, said mounting means including brackets releasably secured to saidflanges.

11. The improvement defined in claim 8 in which said packs arepositioned with each inner sheet of each pack overlapping the sheets ofthe adjacent packs on both sides.

12. The improvement defined in claim 8 in which the supports for a groupof said packs are generally rectangular plates and are arcuately curvedto form sections of a cylinder, the sheets of said group of packs beingconcentrically curved and said group of packs being arranged in acylindrical-heat barrier surrounding said zone.

13. The improvement defined in claim 12 further including interfittingelements on the adjacent edges of said curved supports joining adjacentsupports together in a selfsustaining cylindrical shell.

14. The improvement defined in claim 13 in which said interfittingelements include laterally opening channels on corresponding edges ofsaid curved supports receiving the edge portions of the adjacent curvedsupports.

15. A heat treating furnace having a heating chamber defined by a walledenclosure formed at least in part by a plurality of shield packs ofpreselected size and shape arranged in edge-to-edge relation to form awall of said chamber, each of said packs constituting an independentlyseparable unit having an outer support, a series of reflecting shieldsarranged in spaced side-by-side relation, and means mounting saidshields on the inner side of said support for installation in andremoval from said furnace with said support independently of the othersaid packs.

16. A heat treating furnace as defined by claim 15 in which at leastpart of said packs are generally rectangular in shape.

17. A heat treating furnace as defined by claim 15 in which at leastpart of said packs are in the shape of seg ments of a circle and arearranged in a common plane to form a circular wall.

18. A heat treating furnace as defined by claim in which part said packsare generally rectangular in shape and are arranged around said chamberin a generally cylindrical group, and other packs are in the shape ofsegments of a circle and are arranged in circular groups across the endsof said cylindrical group.

19. A heat treating furnace as defined by claim 18 further includingheating means in said heating chamber including elongated heatingelements spaced inwardly from said rectangular packs and parallelthereto, and means extending through said cylindrical group andsupporting said elements in said chamber.

20. A heat treating furnace as defined by claim 18 in which saidcylindrical group is oriented about a vertical axis, and said supportingmeans include first hangers extending through the upper end portions ofthe rectangular packs and connected to the upper end portions of saidelements, and second hangers below the level of said first hangersbracing the lower portions of said elements.

21. A heat treating furnace as defined by claim 20 in which saidsupporting means also include braces secured at their outer ends toportions of said furnace outside said cylindrical group, said bracesextending inwardly and downwardly to the inner ends of said firsthangers to secure the latter against sagging.

22. A heat treating furnace as defined by claim 20 in which said heatingelements are upright portions of at least one ribbon of resistanceheating material extending zigzag fashion up and down along and aroundsaid cylindrical group of packs, said first hangers being disposedbetween the upper portions of two elements to provide vertical supportand said second hangers being disposed between the lower portions of twoadjacent elements to provide lateral support.

23. A heat treating furnace as defined by claim 15 in which said shieldsare composed of thin and flexible metal foil and said support is ashape-retaining plate, said shields being held generally in the shape ofsaid plate by mounting means including pins on said support extendingthrough the shields, spacers on said pins between adjacent shields, andabutments on the inner ends of the pins holding the inner shields inplace.

24. A heat treating furnace as defined in claim 23 in which said shieldsand said supports are flat rectangular parts.

25. A heat treating furnace as defined in claim 23 in which saidsupports and said shields are arcuately and concentrically curvedwhereby said packs constitute sections of a cylinder.

26. A heat treating furnace as defined in claim 23 in which said curvedsupports are arranged and joined to form a cylindrical shell, eachsupport being removed independently of the others from said shell.

27. A heat treating furnace as defined in claim 23 in which said spacersare helical coils of heat-resistant wire.

28. For use as part of a wall of a heat barrier in a heat treatingfurnace, a radiant shielding pack comprising a series of reflectingshields of preselected shape disposed in spaced, side-by-side relation,said shields being sheets of thin and flexible heat-resistant foil, asupport of shape-retaining material disposed alongside said series ofshields, pins on said support extending through said shields, and meanson said pins maintaining said sheets in properly spaced relation witheach other and with said support for installation in and removal fromthe furnace as a unit.

29. A heat treating furnace as defined in claim 18 in which saidreflecting sheets are sheets of thin and flexible heat-resistant foiland the sheets of one of said packs are in flexible overlappingengagement with the sheets of the adjacent packs on both sides so thatthe inner sheets overlap each other to a greater extent than the outersheets whereby the sheets may be of uniform size for ease ofconstruction.

30. A heat treating furnace as defined in claim 3 in which saidreflecting sheets are sheets of thin and flexible heat-resistant foiland the sheets of one of said packs are in flexible overlappingengagement with the sheets of the adjacent packs on both sides so thatthe inner sheets overlap each other to a greater extent than the outersheets whereby the sheets may be of uniform size for ease ofconstruction.

References Cited UNITED STATES PATENTS 3,002,735 10/1961 Baker et al.263-40 3,033,547 5/1962 Baker et al. 263-40 3,095,494 6/1963 Denton eta1 133 X 3,185,460 5/1965 Mescher et al. 263-40 3,327,041 6/ 1967 Cluneet al 2635O FOREIGN PATENTS 861,257 2/ 1961 Great Britain.

JOHN J. CAMBY, Primary Examiner US. Cl. X.R. 263-50

